Intradialytic hypotension is severely underreported by intermittent blood pressure readings

Background Intradialytic hypotension (IDH) has been associated with both morbidity and mortality. Yet, as IDH often occurs asymptomatic, it might be easily missed with routine twice per hour brachial artery cuff blood pressure (BAC-BP) readings. This study evaluated differences in IDH-detection between intermittent BAC-BP and continuous BP-monitoring with a finger cuff (FC-BP). Validation of the FC-device was an additional objective. Methods In 40 chronic dialysis patients, intradialytic BP was measured during four sessions using 1) BAC-BP every 15 minutes and 2) beat-to-beat FC-BP readings, which were averaged over 20-seconds intervals. IDH was defined as a systolic BP (SBP) < 90 or < 100 mmHg, depending on pre-dialysis SBP. Only FC-measurements with an acceptable accuracy (i.e. mean SBP bias ≤10 mmHg) were used for the IDH analysis. For validation, sequential same-arm BP-measurements were compared, using Bland-Altman analysis to assess agreement and four-quadrant plots to evaluate concordance. Results IDH analysis: A total of 144 BAC-BP readings and 18 163 FC-BP measurements were recorded in 106 hours. While BAC-BP identified 20 IDH-episodes, 441 were detected by FC-BP. Validation: Bland-Altman analysis of 1221 paired BP-readings showed a mean bias ± limits of agreement of -13.3 ± 44.5 mmHg for SBP and -13.3 ± 25.5 mmHg for diastolic BP. Only 27.7% of the paired FC-BP readings met the acceptable accuracy criterion. Concordance rates were 34.3% and 36.3%, respectively. Conclusions First, the occurrence of IDH is severely underestimated with intermittent BP monitoring. Second, FC-BP appears unsuitable for routine intradialytic BP-monitoring due to its poor accuracy, precision and concordance.